The invention concerns a device for metering fuel, preferably two different liquid or gaseous fuels. Such a device is used for example to deliver fuels to the combustion chamber of an internal combustion engine, for example in engines which can be operated with different fuels either alternately or simultaneously.
A device for metering two different fuels is known for example from the unpublished patent application DE 10 2014 225 167 A1. This device, in the form of a fuel injection valve, has two nozzle needles guided inside each other, wherein the outer nozzle needle is loaded with a gaseous fuel, and a liquid fuel, for example diesel fuel, is present in the interior of the outer nozzle needle. A nozzle seat is formed in the interior of the outer nozzle needle, with which seat the inner nozzle needle cooperates in order to open and close inner injection openings, so that on a longitudinal movement of the inner nozzle needle, the diesel fuel can be metered independently of the inflow of gaseous fuel. If gaseous fuels are injected at the same time or at temporally spaced intervals, the outer valve needle moves away from the outer valve seat and exposes injection openings in the nozzle body, through which the gaseous fuel can flow out. If the inner nozzle needle and outer nozzle needle can be controlled separately, both gaseous and liquid fuel can be injected independently of each other, which is important in particular for injecting fuel into a corresponding internal combustion engine which is to be operated with two different fuels.
The production of such a device is however complex since injection openings must be made both in the outer nozzle needle and in the nozzle body itself, in order to allow the through flow of gaseous fuel. If the two fuels are delivered into a combustion chamber in parallel, the additional difficulty arises that the injection openings of the liquid and gaseous fuel must stand in a fixed spatial relationship to each other, in order to configure the combustion optimally. This means that the outer nozzle needle and the inner nozzle needle must be mounted twist-resistantly relative to each other, which entails an additional technical complexity.